Conventionally, there has been known a ventilator in which, the inside of a body casing being open at a bottom surface and having an exhaust port formed on one side is provided with a fan forming airflow toward the exhaust port from an opening of the bottom surface, a resin fan casing of the fan closes the opening of a lower portion of the body casing other than a suction port, a terminal block for connecting input external power supply electric wire to the fan is provided in an internal corner of the body casing and outside an air passage of the fan casing, a protection frame is formed in the fan casing in such a manner that its outer circumferential portion covering the terminal block adheres closely to an inner surface of the body casing and its upper portion is open, and a terminal block cover that watertightly seals a lower portion of the protection frame and can be opened and closed (for example, refer to Patent Document 1).